The invention relates to a heat exchanger, particularly for a motor vehicle.
A preferred field of use of the invention is that of supercharged heat engines, in particular of motor vehicles, which use a particular heat exchanger, further referred to as a charge air cooler (abbreviated to CAC), in order to cool a fluid, that is to say, the charge air of the engine.
This is because supercharged or turbo-compressed heat engines, in particular diesel engines, are supplied with compressed air, referred to as charge air, from a turbo-compressor which is actuated by the exhaust gases of the engine.
However, the effect of that compression is to heat the air which is at an excessively high temperature and it is desirable, for good operation of the engine, to cool it in order to reduce its temperature before it is introduced into the cylinders of the engine.
To that end, there is used, in conventional manner, a heat exchanger which is referred to as a charge air cooler.
The objective of that cooler is to cool the charge air by heat exchange with another fluid such as external air or a liquid such as glycol water of the cooling circuit of the engine, thereby forming an exchanger of the air/air or liquid/air type.
Such a cooler may be fitted in a selected location of the engine compartment, in particular near the engine, and particularly carries out the function of drawing in charge air toward each of the cylinders of the engine.
In known manner, a heat exchanger, and more specifically a charge air cooler, comprises heat exchange elements and fluid flow elements, in which fluids which exchange heat with each other flow.
A large number of associations of fluids may be envisaged, whether liquids and/or gases are involved. In particular, in the case of exchangers, referred to as charge air coolers, it is possible to provide a heat exchange between the charge air, which is intended to supply the engine of the vehicle, and a cooling fluid, in particular a cooling liquid, such as an admixture of water and glycol.
A large number of structural configurations may be envisaged.
There are known exchangers comprising a heat exchange bundle between the two fluids, such as the charge air and the cooling liquid, a receiving casing which receives the heat exchange bundle, and at least one collection tank for the gaseous fluid, such as the charge air, allowing the flow of the charge air through the exchanger.
According to a known solution, the heat exchange bundle comprises a stack of plates which are arranged parallel with each other in one or more rows parallel with each other, those plates being arranged in order to define, on the one hand, first flow channels for a first fluid and, on the other hand, second flow channels for a second fluid, exchanging heat with the first fluid.
Those plates may be alternating with elements for disrupting the flow of a fluid, for example, a gaseous fluid such as charge air.
In a known manner, the plates guide the cooling liquid in a circuit comprising one or more passes. Those plates are generally in the form of an elongate rectangle having two long sides and two short sides, and comprise two projections, a first of the projections having an inlet of the flow circuit for cooling liquid and the other of the projections having an outlet of the flow circuit of the cooling liquid, respectively. The projections are located along the same short side of the plate. The projections of a plate are intended to come into contact with the projections of an adjacent plate in order to allow the cooling liquid to pass from one flow channel to another.
In this manner, the cooling fluid is distributed between the plates by the inlet projections. It subsequently flows along the pass(es) of the flow circuits of the cooling liquid until it is discharged from the plates in the region of the outlet projections.
Each plate thus comprises a heat exchange zone between the cooling liquid and the charge air, which zone is located in the region of the flow pass(es), and an inlet/outlet zone which allows the cooling fluid to be introduced into and discharged from the plates.
A disadvantage of that configuration is that the zone in which the projections are located concentrates mechanical stresses which may bring about a breakage of the elements which are soldered together.
Furthermore, that zone having the projections is very detrimental to the thermal performance. This is because the charge air which passes through that zone does not pass via the exchange zone between the two fluids and therefore does not exchange or barely exchanges any heat with the cooling liquid.
It is known, in order to overcome this problem, to modify the components of the exchanger or to add an additional component which forms a screen and which allows the passage of the fluid to be cooled by that zone to be limited. However, that makes the components and/or the production process of the exchanger more complex, which may involve an additional cost and where applicable an increase in the weight of the exchanger.
In order to overcome those difficulties, there have already been envisaged by the Applicant in a patent application which has not yet been published heat exchangers comprising a cooling fluid collector, which is external with respect to the plates of the heat exchange bundle. The cooling fluid then supplies the heat exchanger, from the collector, via a collector plate through which flow channels of the cooling fluid of the heat exchange bundle open in the collector.
That arrangement requires the provision of enough connection space between the collector plate and at least one closure cover of the collector.
Furthermore, such a collector plate generally comprises flanges which surround the flow channels of the cooling fluid. Those flanges are involved in mechanically retaining the plates of the heat exchange bundle in relation to the casing.
However, those flanges require the provision of additional connection space for assembling the collector plate on the walls of the casing and the closure cover of the collector, which space is substantial.